The present invention relates to a clutch cover assembly suitable for the clutches of automobiles, in which a diaphragm spring is supported by a clutch cover.
The structure shown in FIG. 1 has been known as a coventional clutch cover assembly. In FIG. 1, a clutch cover 2 is secured to a flywheel 1. Stud pins 3 (only one is illustrated) fixed to the cover 2 support diaphragm spring 5 through a pair of wire rings 4 and 4'. Outer radial end portion 5a of the diaphragm spring 5 is in contact with a pressure plate 7 which is operable to press a friction facing of a clutch disc 6 to the flywheel 1. Torque is transmitted from the flywheel 1 through the clutch disc 6 clamped between the flywheel 1 and the pressure plate 7 to a driven shaft (not shown).
The diaphragm spring 5 is designed to have long durability that its load characteristic may change as shown by solid line A in FIG. 2 with respect to its compressed length. Diaphragm spring 5 is generally designed and assembled to have a compressed length at a point B when the clutch is engaged during initial use (i.e., when the clutch is new). However, the facing of the clutch disc 6 wears with long use, which reduces the compressed length of the spring 5 when in the clutch engaged position, so that the load gradually increases to a point C in FIG. 2. Further wear of the facing causes gradual reduction of the load and reduces the length to a wear limit point D on line A. As stated above, the pressing force (load) of the spring 5 increases above the desirable value over long use, especially at about the point C, so that remarkably large and excess torque may be transmitted from the driving flywheel 1 to the driven clutch disc 6. Therefore a transmission mechanism and a differential mechanism of the vehicle must have strength sufficient to bear the excess torque, so that it is impossible to sufficiently reduce the weight of the transmission mechanism and the differential mechanism. Although lightening of the automobile is desirable, the above noted factors prevent lightening of the vehicle. Further, the above described load change causes deteriorating operating feel because pedal force for the clutch pedal becomes heavy when the facing wears to some extent.
Accordingly, it is an object of the invention to provide an improved clutch cover assembly, overcoming the above-noted disadvantages.
The essence of the present invention it to provide a Belleville spring for forcing a diaphragm spring in the compressing direction of the diaphragm spring.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.